The present invention relates to a profile sewing machine for profile stitching to a workpiece in parallelism with an edgeline thereof. More particularly, the invention relates to such profile sewing machine in which a stitching reference line can be visualized on a bed or the workpiece on the bed by a projector etc., the reference line serving as a guide line for sewing a predetermined inward position of the workpiece in parallelism with the edgeline of the workpiece.
Profile sewing has been conventionally carried out in which swing needle location is positioned at a predetermined inward position of the workpiece fabric relative to the edgeline thereof, so that a seam or stitching line is oriented in parallel with the edgeline. For facilitating the profile sewing, one conventional profile sewing machine has been proposed in which the sewing needle can be automatically moved laterally at the predetermined inward position of the workpiece fabric in such a manner that the needle location is automatically changed to maintain parallelism with the edgeline of the workpiece fabric in accordance with a result of detection to a position of the edgeline.
Such profile sewing machine is described in, for example, Japanese Patent Application Kokai No. 62-68483. The profile sewing machine includes a needle bar, a needle bar swinging mechanism, a workpiece fabric detector and control means. The needle bar has a lower end securing a sewing needle, and is movable in a vertical direction as well as a lateral direction with respect to feeding direction of the workpiece fabric. The needle bar swinging mechanism is adapted for swinging the needle bar in the lateral direction within a predetermined stroke range. The workpiece fabric detector is adapted to detect the edgeline of the workpiece fabric. And the control means is adapted for controlling the movement of the needle bar swinging mechanism in order to provide a needle location at a proper inward distance from the workpiece edgeline.
With the structure, the sewing needle can follow the workpiece fabric in the lateral direction even if the latter is laterally deviated during the profile sewing operation. Therefore, maintainable is a constant distance between the workpiece edgeline and the needle location, to thereby provide a constant or uniform stitch margin (the distance between the edgeline and the exact needle location or exact stitched line will be referred hereinafter as the term "margin").
Further, prior to the profile sewing, the sewing needle can be automatically moved toward the seam or stitching position when the workpiece fabric is mounted on the bed. However, in such conventional sewing machine, if the deviation of the workpiece fabric exceeds a predetermined level during the profile sewing, the sewing needle cannot follow the deviation, to thereby render the automatic profile sewing inoperative. In such case, the sewing operation is temporarily suspended or the sewing speed is lowered, and then, the workpiece fabric is manually moved so as to correct the lateral position of the sewing needle or the needle location in response to the lateral movement of the workpiece. When correction work is carried out for correcting the position of the workpiece fabric, it would be rather difficult for an operator to make judgment as to the laterally deviating direction of the sewing needle. As a result, a long time period may be required for the positional correction.
Then, improvement is made on such conventional profile sewing machine in an invention disclosed in Japanese Patent Application Kokai No. 1-115469. The improved sewing machine is provided with instruction means for instructing direction in which the sewing needle is to be moved in order to correct the deviation or for instructing the deviating direction of the sewing needle. The improved sewing machine includes, in addition to the mechanical and electrical components equipped in the conventional sewing machine described in the above described JP 62-68483, a detection means and the instruction means. The detection means detects the deviating direction of the sewing needle with respect to a center position of a swingable range of the needle, and the instruction means instructs the deviating direction of the sewing needle or correcting direction of the needle in accordance with a result of the detection by the detection means. The instruction means includes a plurality of display lamps arranged on a main body of the sewing machine, which lamps indicate the deviating direction or deviation-correcting direction. Further, a front ruler is conventionally used for guiding travel of the workpiece fabric so as to obtain uniform stitching margin, and the ruler is also available in the profile sewing machine.
However, when correcting the needle location in accordance with the deviation of the workpiece fabric during profile sewing operation, the improved sewing machine still has a problem in that it would be difficult for an operator to make judgment as to a proper correcting position from the deviated position. In the sewing machine described in the above described JP 1-115469, since the deviating direction and the deviation-correcting direction are displayed by the lamps arranged on the main body, the operator, who draws her particular attention to the sewing needle and the workpiece edge, must also turn her eyes upon these lamps in sewing operation in order to note the deviating direction and the deviation correcting direction.
Further, in the method using the front ruler, the ruler must be provided at a precise position, otherwise sufficient profile sewing cannot be attained. Particularly, if the workpiece has a continuous curving edgeline, it would be extremely difficult to determine the suitable setting position of the ruler.
For the purpose of information, a commonly assigned U.S. patent application Ser. No. 07/602,699 has been filed on Oct. 24, 1990. Further, sewing machines of relevant field have been described in U.S. Pat. Nos. 4,248,168, 4,664,048, 4,823,716, 4,827,858 and 4,869,189.